Electric Dipole: S.H.O

(This question doesn't apply to a specific problem, hence I'm not using the template.)

Consider a dipole, approximated as a "dumbbell": two oppositely-charged spheres (charges of equal mag.) connected by a rod (that is, the chemical bond). Suppose that I know the dipole moment. If this dipole is placed in a uniform electric field, then it would experience a net torque (but no net force).

I would like to know how I could calculate the period of the dipole's oscillations in this field? Given the electric field (vector), I know to calculate the torque (τ = p X E). From here, however, I don't know how I might use this information to calculate the period/freq. of the dipole's S.H. Oscillation. Any advice?